Re: help! 96 f150 fails emissions test

#1

"salty_dogs" <salty_dogs (AT) hotmail (DOT) com> wrote

Quote:

i think it all comes back to a lean mixture... weak fuel pump?clogged fuel
filter?
any ideas?

Sounds like it. But I doubt it's the pump or filter. Otherwise all
cylinders should be doing it. I'd take a good look at the EGR as a
matter of course, and then injector flow, etc...Make sure your engine
is not "carboned up". That will cause this problem due to the semi
clogging of the injectors, and higher compression due to the carbon in
the chambers. Also carbon can soak fuel vapors, and cause a lean
problem. I'd run a can or two of techron fuel system cleaner through
it, and do as much stop and go driving as possible. IE: get the truck
hot, and then shut it off and let the techron heat soak the injectors
and chambers, intake valves etc. Do that over and over if possible.
Running injector cleaner does nothing for a running engine. All the
"work" is done on each heat soak while the engine is hot and sitting.
This is the same way the carbon and gunk builds up in the first place.
Anyway, you do sound lean, but it's just a guessing game without
seeing it. I'd check everything emmision related including temp
sensors, O2 sensors, the whole ball of wax. Being it's on random
cylinders, I'm guessing towards some carbon, and semi clogged
injectors. You might be able to visually verify if you can locate a
borescope. We had the same problem on a camry recently. MK

#2

Your 96 (and newer) vehicles are OBD 2.
You have 02 sensors before and after the cat converter(s)
teh computer reads both 02 sensors and calculates a) emiisions
performance, b) cat converter function.

In your case, the cat code indicates a problem. In most cases, the
Ford tech will follow a diag chart based on the code(s) present and
perform other tests (is 02 sensor reading, etc). sometimes they
reprogram the computer to calculate differently. Most likey you need a
cat converter, sorry.

you could try Midas, Meineke, etc and save some mony that way.

chris

On Sat, 21 Jun 2003 20:07:08 -0400, "salty_dogs"
<salty_dogs (AT) hotmail (DOT) com> wrote:

Quote:

i have a 1996 F150 with about 120k miles. its a 4.9 6cyl. that i've owned
since 30k miles. the check engine light has come on and stayed on for a
while now. i took it in for service about a year ago and they said: 'a new
cat conv. was needed' they (a dealer) said it was gonna be about 1000
clams. no thanks.

i guess i should have investigated a little further then but i got the codes
from the obd/eec computer yesterday:

1. po174 - system (adaptive fuel) too lean (bank #1)
2. po420 - catalyst system efficiency below threshold (bank #1)

so the service dept. at the dealer reads this (a year ago) and tells me the
catalytic converter is shot.

last week i took the truck in to get an inspection sticker, and what do you
know? i fail the emissions test. what was i thinking? here's the results:

hc gpm .20 (2.25 limit)
co gpm 2.78 (20.84 limit)
nox gpm 3.79 (2.92 limit)

it failed the nox. so i pull out the test that was done two years ago at 90k
miles:

hc gpm .68
co gpm 5.34
nox gpm 1.05

ok, this kinda makes sense. i have a lean (hot) burning engine now, that is
lowering my hc and co levels but increasing my nox. but this doesn't account
for a 'bad' cat.conv. does it? i would think that the cat. is ok and if the
engine temp was lowered during cruise, this would result in lower nox level.
right? this of course leads me to believe that the egr valve or its related
mechanism (tubes) is not getting enough exhaust gas back into the intake
manifold. yet, there is not egr error. my understanding is that the
cat.conv. takes care of nox as a secondary function. combustion temperature
is the primary way of controlling nox emissions.

i think it all comes back to a lean mixture... weak fuel pump?clogged fuel
filter?
any ideas?

Crispy

Life is hard.
Life is harder when you're stupid.

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Re: help! 96 f150 fails emissions test

Ford Vehicles Discussions About Ford Cars (alt.autos.ford)

Re: help! 96 f150 fails emissions test - 06-22-2003 , 01:39 AM

Re: help! 96 f150 fails emissions test - 06-22-2003 , 07:42 AM